The present invention relates to a power unit of an underwater vehicle.
Underwater vehicles used for investigation, search and the like in the sea and water are broadly classified into an untethered type underwater vehicle which operates automatically and a tethered type underwater vehicle connected with a mother vessel which conveys and operates the underwater vehicle through a cable as disclosed for example in JP-A-H09-272494. Each of the underwater vehicles is used in a scene according to its characteristic.
Out of those underwater vehicles, the cable type underwater vehicle has the advantage of being capable of easily performing power supply and information communication through a cable since it is connected with the mother vessel through the cable.
However, in recent years, the development is underway on an underwater vehicle which enables search at a depth as great as about 10 km, and the like. Such an underwater vehicle requires a cable about twice as long as the depth in consideration of water flow and the like. When power is supplied using such a long cable, electric resistance is naturally large, and hence a high voltage power supply is installed on the mother vessel so as to reduce voltage drop (power loss).
When the high voltage power supply is used, it is necessary on the underwater vehicle side to decrease the voltage according to devices loaded thereon, and for this reason, a transformer is loaded on the underwater vehicle.
A transformer loaded on a conventional underwater vehicle is a so-called winding transformer. This winding transformer has the property of increasing in size and weight in proportion to an increase in power consumption.
Meanwhile, on the underwater vehicle, a propeller such as a thruster, observation devices such as an underwater camera and sonar, and an operational device such as a manipulator, and the like, are loaded. It is preferable in terms of obtaining a favorable operating environment to increase a loading amount and variety of those devices since it leads to enhancement of searching performance and the like.
However, there is a limit (payload limit) to weight of devices loadable on the underwater vehicle, including the winding transformer. When the number of loaded devices increases, not only the weight but also power consumption increases. With that increase, the winding transformer is increased in size and weight. It is therefore practically difficult to increase the loading amount of the devices within the payload limit range.